Hailu Tolossa Yacob

Ectoparasites of small ruminants in three selected agro-ecological sites of Tigray Region, Ethiopia

A study on ectoparasites of small ruminants in three selected agro-ecological sites of Tigray Region, Ethiopia disclosed an overall prevalence of 55.5% and 58% in each examined 750 sheep and goats, respectively. In the sheep population, Melophagus ovinus (19.1%), tick infestations (16%), Damalinia ovis (15.3%), Linognathus africanus (11.5%), and Ctenocephalides felis (9%) were the major ectoparasites. The major ectoparasites identified in goats were tick infestations (29.7%), L. africanus (27.9%), Sarcoptes scabiei var. caprae (12.5%), C. felis (11.1%), and Demodex caprae (6.8%). In sheep, there was a statistically significant difference (P < 0.001) in the prevalence of Damalinia ovis, M. ovinus, L. africanus, and ticks between midland and highland. In goats, the risk of Sarcoptes scabiei var. caprae infestation in midland (odds ratio (OR) = 17.2, P < 0.001) and lowland (OR = 5.2, P < 0.001) was 17.2 times and 5.2 times, respectively, higher than the highland. Favorable climatic conditions, backward level of management, poor level of consciousness and awareness of farmers, and weak animal health extension services are believed to have contributed for widespread distribution and occurrences of ectoparasites. The growing threat of ectoparasites to small ruminant production and the tanning industry needs well-coordinated and urgent control intervention.

Efficacy of Cymelarsan® and Diminasan® against Trypanosoma equiperdum infections in mice and horses

Trypanocidal sensitivity studies were conducted to assess the efficacy of Diminazene diaceturate (Diminasan) and Bis (aminoethylthio) 4-melaminophenylarsine dihydrochloride (Cymelarsan) against Trypanosoma equiperdum (isolated from two mares with chronic cases of dourine) 713/943 and 834/940 Dodola strains in experimentally infected mice and horses. Diminasan at doses from 3.5 mg/kg to 28 mg/kg and Cymelarsan at doses of 0.25 mg/kg and 0.5 mg/kg body weight failed to cure any of the mice, indicating a clear dose dependent relationship in the mean time of relapse observed in mice. Indeed, mice treated with lower doses relapsed after a shorter time than mice treated with higher doses. However, mice treated with Cymelarsan at doses of 1.0 mg/kg and 2.0 mg/kg body weight were cured and no parasitemia was observed for 60 days. The efficacy of Cymelarsan was also tested in horses. Two groups of horses containing two animals each were infected with T. equiperdum 834/940 Dodola strain and treated with Cymelarsan at a dose rate of 0.25 mg/kg and 0.5 mg/kg, respectively. Cymelarsan at 0.25 mg/kg and 0.5 mg/kg body weight cleared parasitemia within 24 h post treatment and none of the animals were found to show relapse throughout the 320 days of observation. The sensitivity of the particular trypanosome strain to Cymelarsan was also supported by the relative improvement in the mean PCV levels of horses following treatment. A statistically significant difference (p<0.01) in the mean PCV levels of horses treated with Cymelarsan was observed between day 20 at peak parasitemia and days 40 as well as 60 of observation. The mean PCV levels of horses in the control group progressively decreased within the first 60 days of post infection. Two of the horses in the control group developed chronic form of dourine manifested by genital as well as nervous signs with progressive loss of body condition within 320 days post infection. The efficacy of Cymelarsan against the chronic form of dourine was confirmed after treatment of one of the control horses with Cymelarsan at a dose rate of 0.25 mg/kg body weight at day 282 post infection. It was noted that the treated horse improved overall body condition and clinical signs such as incoordination of hind legs, weakness and ventral oedema disappeared within 10 days of treatment. Thus, Cymelarsan was found to be quite effective in curing horses in acute as well as chronic form of dourine. The results obtained from the present study will be important for designing effective control measures against dourine.

Parasitological and clinical responses of lambs experimentally infected with Haemonchus contortus (L3) with and without ivermectin treatment

Haemonchus contortus is one of the most important parasites that infects sheep and exerts its pathogenic effects by sucking blood, causing disturbances of organ-functions and thus inducing alterations in various normal physiological parameters. Changes in live body weight, faecal egg count, kinetics of circulating eosinophils and PCV value were studied at weekly interval for a period of 84 days in 18 lambs of local breed after infection with a single dose of 5000 H. contortus (L(3)). In the two groups of lambs infected with nematodes both non-treated and treated with ivermectin (HcNT and HcIT), similar egg excretion patterns was observed starting from third week after infection, with a regular increase in FEC. Examination of whole abomasum of each animal revealed no developmental stage of nematode from treated and control lambs on day 84. The total mean number of H. contortus worms recovered at necropsy from abomasa of untreated infected lambs (group HcNT) was 2576.2 (+/-221.0). The significant loss of body weight, development of heavy worm burden and severe anaemia as indicated by reduced PCV in untreated infected lambs indicated high susceptibility of the lambs to H. contortus. On the other hand, complete absence of the parasite, improved PCV value and body weight after treatment of infected animals (HcIT) proved 100% efficacy of ivermectin against H. contortus.